Heat exchangers intended to be buried in the ground for use with ground source heat pumps are well known, particularly for buildings, and are of two kinds, horizontal and vertical.
The horizontal type involves the placement of one or more pipes horizontally in a relatively shallow trench, the pipes being buried from three to six feet deep or more, and spaced apart either horizontally or vertically, or both. The disadvantage of this arrangement is that the trench must be rather long in practice, ranging from 50 feet per ton rating of the heat pump to 500 feet per ton rating depending on the specific design involved. The systems requiring shorter trenches have greater market potential than systems having longer trenches, but all these horizontal systems are restricted by the requirement for an appropriate pipe installation space and they are virtually restricted to rural properties or relatively large urban lots.
The vertical type of ground coil has two basic variations. The first and most common must be installed in a borehole of relatively small diameter which may extend into the ground for more than 100 feet. Ground coils which may be installed to a smaller depth are rare, and are undesirable because of the increased complexity of the headers required. The main disadvantage of the vertical installation is that it permits the introduction of contaminants along the borehole into the aquifer. This is a significant disadvantage because the boreholes are not sealed, only filled. For this reason, this type of system has already been prohibited by legislation in some jurisdictions. The second type of vertical ground coil requires medium sized boreholes of from twelve to forty-eight inches in diameter, but still may require to be installed to a depth of fifty feet even for a relatively small system. The equipment used to make such boreholes is prone to damage by boulders or other obstructions.
It is an object of the present invention to provide a ground coil assembly for use in association with a ground source heat pump, which does not have to be installed to a great depth and which takes up only a small ground area.
Another object of the invention is to provide such a ground coil assembly which can be easily packed and shipped in a small size and which is particularly easy to instal.